Dear Ari Leflein,
Thank you for posting your inquiry on History Hub!
We searched the National Archives Catalog for any record on the Advisory Board on Clemency and located the following results.
In particular, within the Records of the U.S. High Commissioner for Germany (Record Group 466), there are 2 file units located in the series “Security-Segregated Records, 1945-1957” that might be of relevance to your inquiry.
Please note that due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of our staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from the Truman Library and RDT2. We apologize for this inconvenience and appreciate your understanding and patience.
We hope this information is helpful. Best of luck with your research!